I would have thought that if the plaster section is kept to a minimum and the pour is done straight after a damn good heating in the furnace (or whatever), wouldn't that solve any cracking problems? - then again I could very well be wrong!
I would have thought that if the plaster section is kept to a minimum and the pour is done straight after a damn good heating in the furnace (or whatever), wouldn't that solve any cracking problems? - then again I could very well be wrong!
Strokers Galore!
Some success and some failure.
The casting I actually wanted came up short
The surface area verses in gate size was not matched well with the fill happening too slow with too much cooling on all the thin sections. Solidified before filling the mold. Both molds, same fault.
The rest turned out ok.
Saw an american website where he was investment casting with "dry-wall mud", whatever that is.
google.............Alpha Gypsums calcined under pressure are called gypsum cements - These Alpha Gypsum casts are harder and stronger with limited absorptive power. They require 22 to 45 lbs of water per 100 lbs of gypsum cement (this is called the Use Consistency Ratio). They are used primarily when greater strength is required. Because of their extreme hardness some Alpha gypsums can not be carved or scraped after hardening. Alpha Hemihydrate is produced in many different formulations. You can mix an alpha gypsum with a beta gypsum such as moulding plaster to increase the plaster's strength or hardness. I use 3 scoops of plaster to one scoop of HYDRO-STONE in my sculpted model work. To help you choose the ones that best suits your needs, check out the list below.
Beta Hemihydrates are known as industrial plasters, plaster of paris, kettle plaster and kettle stucco. Beta Gypsums are made by calcining in a kettle at atmospheric pressure. They require more water to make a workable slurry because of their irregular crystalline structure. They require 65 to 160 lbs. of water per 100 lbs of plaster ( consistency ratio). Beta Gypsums are not as hard as the alpha gypsums. That's why they are easier to carve and scrape. Because of their high water absorptive power, they make excellent pottery molds. There are many beta Gypsums from which to choose. Use the list below to help you in making your decision
Interesting stuff and I have similar information in a suppliers catalogue but doesn't tell cheapskates like me if eg. UK finishing plaster is the same as the US sheetrock. I'm away from home and wi-fi too so using the internet burns through my phone credit...
Never the less, I have found the site I was on about as googling "aluminum casting submarine" was a pretty sure bet!
www.submarineboat.com/casting_aluminum.htm
Got it, in the pile with the rest, off to heat treatment this week.
Wooden core box copied into metal so as to make Shell Sand cores, much stronger and easier to manufacture, I just use capscrews to hold the die together. Spend a little time with bearing blue and my small die grinder to get a nice fit.
This water core is to suit this cylinder.
Guess shellsand is the best way to go, but I do hope your "cooker" isn't too near the house!
Will you still be using graphite for a release agent?
Have you considered making the external moulds with shellsand?
I remember seeing brass bathroom fittings and various bronze valves being produced from shellsand moulds (with shellsand cores) - and saw some very good castings appear at the end.
Strokers Galore!
I send these castings away, its a an exact process and I'm not willing to risk wreaking them.
With my business I get a lot of CC601 cast and heat treated, I just tack these home cast units on to a treatment run.
Out of interest the treatment involves heating the casting to almost melting for something like 16 hours then when time is up, they get quickly quenched in 80 degree C water.
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